Aftertreatment of tows consisting of continuous artificial filaments



p 1960 MAX-OTTO SCHURMANN 2,953,424

AFTERTREATMENT OF TQWS CQNSISTING OF CONTINUOUS ARTIFICIAL FILAMENTSFiled Dec. 13, 1954 IN VEN TOR. MAX orro SCHURMANN BY 35 .Mk

A T TORNE KS United States PatentOfiice AFTERTREAIMENT OF TOWSCONSISTING OF CONTINUOUS ARTIFICIAL FILAMENTS Max-Otto Schiirmann,Dormagen, Germany, assignor to Farbenfabriken Bayer Akfiengesellscllaft,Leverkusen, Germany, a corporation of Germany Filed Dec. 13, 1954, Ser.No. 474,763

Claims priority, application Germany Feb. 15, 1954 '3 Claims. (Cl.8151.2)

The invention relates to the chemical processing and washing of towsconsisting of continuous artificial filaments.

The continuous production of tows consisting of artificial filaments ofregenerated cellulose is in principle similar to the production of rayonyarn by the continuous process. The thickness of the tows is however,much greater than that of the yarn. This greater thickness of the towsrenders any wet treatment thereof extremely diificult because itrequires a multiple of the time of the wet treatment of yarns.

It is therefore an object of the present invention to provide a processfor the aftertreatment of tows consisting of continuous artificialfilaments, by which the Wet treatment can be performed in a short periodof time.

A further object is the provision of a process for the aftertreatment oftows of filaments with the utmost economy in chemicals.

A still further object consists in a process, which avoids the stickingof individual filaments to each other in the tow. Another object residesinthe provision of a process by which cuprammonia cellulose filamentscan be acidified and freed of copper in a short space of time andwithout the danger of sticking.

Another object is the provision of an apparatus for continuouslyaftertreating tows of artificial filaments, which requires little spaceand is easy to handle.

Still further objects will become apparent as the followingspecification proceeds.

These objects are accomplished according to the invention by applyingthe treating liquid to the tow vertically with high speed in fine jets,the tow itself being kept under as small a tension as possible.

In order to counteract the displacement of filaments it is necessary togive the tow a support, for instance by placing it on an endless movablesieve. This sieve should move with a slightly slower speed than the towwhich it supports in order to obtain the necessary lack of tension andto allow the tow to shrink unhindered.

Preferably the tow is laid on the horizontally moving sieve and thetreating liquids are applied thereto through nozzles or sprays disposedat a small distance thereover. The diameter and speed of the liquid jetsmust be kept within predetermined limits; jets which are too coarse andstrong lead to an undesirable displacement of the filaments while finejets may lead to a stopping of the fine holes of the nozzles and slowjets fail to produce the optimum effect. The number of holes and theirdistance from each other should be so selected that the cable is notcovered by any substantial amount of liquid. The distance from thesprays of the material to be treated is of importance since it has aninfluence on the speed of the jets. In selecting the speed and strengthof the jets (the first of which is substantially dependent upon thepressure of the liquid in the spray), the thickness of the tow and alsothat of the individual filaments must be taken into consideration. Thicktows require a more intense treatment than thin ones.

With a thickness of the tow of from about 30,000 to about 100,000deniers and an individual denier of 2. to 6, a diameter of the holes of0.3 to 0.8, preferably 0.5 millimeter, a pressure of the aqueous liquidof between about 0.3 to 1.5, preferably 0.5, atmospheres above normaland a distance of the sprays from the tow of from 5 to 15 centimeters,preferably 10 centimeters, has proved effective. The number of holesamounts to about per square decimeter.

As a support, a sieve band having the greatest possible permeability isemployed in order to enable the washing liquid to run unhinderedtherethrough. Woven sieves or spiral wefts from stainless steel haveproved particularly effective.

The single figure of the accompanying drawing shows a diagrammaticcross-sectional view of the apparatus employed. A set of rollers 1 isdisposed at the entrance side of the apparatus. A sieve band 2 mountedon rollers 3 is arranged beneath a plurality of sprays or nozzles 4,which are connected with the pump 5 by the pipe 6 ending in tube 7.Beneath the movable sieve band there is arranged a tray '8 whichcollects the liquid coming from the sprays and in which this liquid ismixed with fresh treating liquids from tap 9.

In operating the apparatus, the tow t is introduced by means of the setof rollers 1, running at a peripheral speed slightly higher than thespeed of the sieve band 2. Thus the tow is laid on the sieve bandwithout any tension. The sprays are then operated by starting the motorof pump 5 whereupon the jets of liquid from the sprays are directedagainst the tow. The liquid passes through the sieve and'is collected inthe tray 8. It is again concentrated from tap 9.

Apart from the saving of time already mentioned, the process of theinvention has the advantage of requiring considerably less room for theapparatus and providing for a more efiicient use of the chemicalsemployed. The invention replaces washing by dilution by Washing bydisplacement. The invention further saves the complicated stirringmechanism which was necessary hitherto in order to keep up a slighttension when tows are washed in long containers. The process is welladapted for hardening freshly spun tows from regenerated cellulosefilaments which are apt to adhere to each other. It is especially usefulin removing copper from tows freshly spun from cuprammonia cellulosesolutions.

The acidifying of the blue fiber with dilute sulfuric acid is one of themost complicated steps in cuprammonia fiber production since the fiberhere passes through a state in which it has a maximum tendency to stick.While according to hitherto known methods it was diflicult to obtain aproduct free from cohering sections, the present process yields aproduct which is entirely free of cohesion. The time required foracidifying is about of that required according to the known methods.This favorable behavior as regards lack of tendency for sticking makesit possible to reintroduce a higher percentage of used precipitatingliquid containing ammonia and copper into the process, which renders theprocess more economical as regards consumption of chemicals. Theprecipitating liquid which is reintroduced into the process may bewholly or partly freed of copper by leading it over a cation exchangeresin. The process further allows a reduction of the temperature of thespinning bath, a fact which leads to economy in steam consumption. Thefurther washing of the tow after the removal of the copper may befurther accelerated by applying the principles of the invention.

The final washing may be carried out in the same step on the same sieveband or after squeezing out the liquid on a separate sieve. The dryingof the tow may be effected by applying thereto a vertical stream ofheated air Patented Sept. 20, 1960 of high speed. The advantages of thiscombined method allow the tow to be continuously processed to the finalstages on a very short length of apparatus. A further advantage consistsin the complete lack of displacement of individual filaments which wouldlead to difiiculties in the continuous tearing or cutting of the towinto staple. Furthermore it is possible to use the shrinking duringacidification and drying to obtain a structural crimp.

I claim:

11. The process of continuously aftertreating a tow consisting of abundle of filaments of regenerated cellulose and having a thickness offrom about 30,000 to about 100,000 deniers with a titer of theindividual filaments of from about 2 to about 6 deniers, which processcomprises continuously feeding said tow onto a moving endless sieve bandand directing thereagainst vertical jets of liquid under asuperatmospheric pressure of from about 0.3-1.5 atmospheres gaugethrough nozzles having a plurality of holes with a diameter of fromabout 0.3 to 0.8 millimeter, said nozzles being disposed at a distanceof 5 to 15 centimeters from said sieve.

4 2. A process according to claim 1 in which the filaments are spun froma cupramrnonia cellulose solution.

3. A process according to claim 2 in which the filaments are freshlyspun and still in the alkaline state and liquid is dilute sulfuric acid.

References Cited in the file of this patent UNITED STATES PATENTS338,096 Meikle Mar. 16, 1886 455,059 Sargent June 30, 1891 1,269,340Vander Kleed et al. June 11, 1918 2,267,117 Mann Dec. 23, 1941 2,520,594Costa Aug. 29, 1950 2,698,625 Bitzer I an. 4, 1955 FOREIGN PATENTS632,975 Great Britain Dec. 5, 1949 666,188 Great Britain Feb. 6, 1952707,419 Great Britain Apr. 14, 1954

1. THE PROCESS OF CONTINUOUSLY AFTERTREATING A TOW CONSISTING OG ABUNDLE OF FILAMENTS OF REGENERATED CELLULOSE AND HAVING A THICKNESS OFFROM ABOUT 30,000 TO ABOUT 100,000 DENIERS WITH A TITER OF THEINDIVIDUAL FILAMENTS OF FROM ABOUT 2 TO ABOUT 6 DENIERS, WHICH PROCESSCOMPRISES CONTINUOUSLY FEEDING SAID TOW ONTO A MOVING ENDLESS SIEVE BANDAND DIRECTING THEREAGAINST VERTICAL JETS OF LIQUID UNDER ASUPERATMOSPHERIC PRESSURE OF FROM ABOUT 0.3-1.5 ATMOSPHERES GAUGETHROUGH NOZZLES HAVING A PLURAITY OF HOLES WITH A DIAMETER OF FROM AOBUT0.3 TO 0.8 MILLIMETER, SAID NOZZLES BEING DISPOSED AT A DISTANCE OF 5 TO15 CENTIMETERS FROM SAID SIEVE.